1 /* 2 +----------------------------------------------------------------------+ 3 | Copyright (c) The PHP Group | 4 +----------------------------------------------------------------------+ 5 | This source file is subject to version 3.01 of the PHP license, | 6 | that is bundled with this package in the file LICENSE, and is | 7 | available through the world-wide-web at the following url: | 8 | https://www.php.net/license/3_01.txt | 9 | If you did not receive a copy of the PHP license and are unable to | 10 | obtain it through the world-wide-web, please send a note to | 11 | license@php.net so we can mail you a copy immediately. | 12 +----------------------------------------------------------------------+ 13 | Authors: Rasmus Lerdorf <rasmus@php.net> | 14 | Zeev Suraski <zeev@php.net> | 15 | Pedro Melo <melo@ip.pt> | 16 | Sterling Hughes <sterling@php.net> | 17 | | 18 | Based on code from: Shawn Cokus <Cokus@math.washington.edu> | 19 +----------------------------------------------------------------------+ 20 */ 21 22 #ifndef PHP_RAND_H 23 #define PHP_RAND_H 24 25 #include "php_lcg.h" 26 #include "php_mt_rand.h" 27 28 /* System Rand functions */ 29 #ifndef RAND_MAX 30 #define RAND_MAX PHP_MT_RAND_MAX 31 #endif 32 33 #define PHP_RAND_MAX PHP_MT_RAND_MAX 34 35 /* 36 * A bit of tricky math here. We want to avoid using a modulus because 37 * that simply tosses the high-order bits and might skew the distribution 38 * of random values over the range. Instead we map the range directly. 39 * 40 * We need to map the range from 0...M evenly to the range a...b 41 * Let n = the random number and n' = the mapped random number 42 * 43 * Then we have: n' = a + n(b-a)/M 44 * 45 * We have a problem here in that only n==M will get mapped to b which 46 # means the chances of getting b is much much less than getting any of 47 # the other values in the range. We can fix this by increasing our range 48 # artificially and using: 49 # 50 # n' = a + n(b-a+1)/M 51 * 52 # Now we only have a problem if n==M which would cause us to produce a 53 # number of b+1 which would be bad. So we bump M up by one to make sure 54 # this will never happen, and the final algorithm looks like this: 55 # 56 # n' = a + n(b-a+1)/(M+1) 57 * 58 * -RL 59 */ 60 #define RAND_RANGE_BADSCALING(__n, __min, __max, __tmax) \ 61 (__n) = (__min) + (zend_long) ((double) ( (double) (__max) - (__min) + 1.0) * ((__n) / ((__tmax) + 1.0))) 62 63 #ifdef PHP_WIN32 64 #define GENERATE_SEED() (((zend_long) ((zend_ulong) time(NULL) * (zend_ulong) GetCurrentProcessId())) ^ ((zend_long) (1000000.0 * php_combined_lcg()))) 65 #else 66 #define GENERATE_SEED() (((zend_long) ((zend_ulong) time(NULL) * (zend_ulong) getpid())) ^ ((zend_long) (1000000.0 * php_combined_lcg()))) 67 #endif 68 69 PHPAPI void php_srand(zend_long seed); 70 PHPAPI zend_long php_rand(void); 71 72 #endif /* PHP_RAND_H */ 73
